Motor control and phasing



April 8, 1941. po 's I 2,237,951

MOTOR CONTROL AND PHASING All vvv' I W INVENTOR.

n LOUIS M. POTTS ATTORNEY.

April 8, 1941. L. M. POTTS MOTOR CONTROL AND PHASING Filed July 3, 1937 2 Sheets-Sheet 2 INVENTOR. LOUIS M. POTTS Patented Apr. 8, 1941 MOTOR CONTROL AND PHASING Louis M. Potts, Evanston, Ill., minor to Teletype Corporation, Chicago, 11]., a corporation of Delaware Application July 3, 1937, Serial No. 151,827

13 Claims.

The present invention pertains to telegraphic communication systems and more particularly to telegraph systems involving a plurality of substations arranged upon a plurality of radial lines which connect a central oillce with the substations which are provided with telegraph apparatus havirm a driving motor normally inert.

An object of this invention is to maintain synchronism of a substation driving motor by the use of alternating currents transmitted from a central oiilce over a communication line but independently of communication signals transmitted over the line.

A feature of the invention is the provision of means associated with the switching devices at the central oiilce and with the motors of the substations such that a substation motor is started into operation in response to seizure of its connecting line by the central oili'ce switching equipment and in which synchronous motors may be started by an alternating current of low frequency which is increased to the full operating frequency of the motor, the motor being thereafter maintained in synchronism by a continuous alternating current supplied over a power circuit or synchronizing circuit which is operatvely independent of communication signals.

Further features reside in provision of means for restarting substation motors automatically,

should they have been stopped, in the provision 1 of auxiliary means for supplying power to the substation motor. and in the provision of starting means changeable dependently upon increasing speed of the motor to synchronizing speed.

These objects and features are attained by supplying at the central office embodied in interconnective devices a source of alternating current which supplies the synchronizing power over a power conductor or over the communication conductor or over phantom or composited circuits after a communication condition has been established and over various circuits in the steps of progress toward establishment of the communication condition, and by providing further means in the connective equipment at the central office for supplying an alternating current of varied frequency, this further means also being operative to supply to a line a polyphase current comprising a series of impulses of alternating polarities and oi! increasing frequency in response to seizure of the line for communication purposes.

A more complete understanding of the invention will be obtained from the following description taken in connection with the accompanying drawings, in which Fig. 1 illustrates a complete equipment of one central oflice connective unit associated with two line jacks and one substation;

Fig. 2 illustrates a modification embodying a self-starting substation motor with automatic starting switches and circuits;

Fig. 3 illustrates a central oiilce connective unit and a substation having a synchronous motor with an auxiliary source of power;

Fig. 4 illustrates cam 11 of Fig. l; and

Fig. 5 illustrates pivoted armature lever 68 of Fig. 1.

In Fig. 1, a connective pair of plugs i and 2 are connected for communication through a repeater relay set 3 when relays 5 and 8 are energized, and the circuits of the connective plugs also include inductive association with a source of alternating current when connective relays 6 and 6 are energized. Prior to energization of relays and 8 respectively, the switching plugs i and 2 are connected to output conductors of a generator I which normally is at rest, but which is energized to start into rotation when plug i or plug 2 is inserted into a line jack such as 8. The generator 1 then delivers to line conductors associated with the line jack and plug, a polyphase current comprising two concurrent series of alternating current impulses generated by its commutator 9, the frequency of which increases as the speed of the generator i increases, until this increasing frequency attains the frequency of the alternating current source it after which relay 5 is operated to switch the conductors of plug i through to the alternating current source in and to the repeating relay set 3.

At substation ii, a synchronous motor i2 is provided with a centrifugal device it having a switch I with a plurality of contacts which are shown in contactuai relations of their condition of rest. The centrifugal device has also a cam contact i5 which is operated by a rotating cam 11 effective at low speeds of motor 82 as shown in solid line in Fig. 4, but withdrawn as shown in dotted line, by the centrifugal device i3 when motor i2- is rotated at higher speeds. A printer selector magnet is symbolized at it, a permutation code signal transmitter is symbolized at ii, a calling key is illustrated at i8, and a condenser i9 is included in an alternating current power circuit of motor i2 to prevent operation of series relay winding I06.

At the central oflice, the radial substation communication line 2i is provided with a switching jack 8 and a signaling line relay 22 which has a line lamp 23 and a cut-off relay 24. Specific circuits for the described apparatus will be identified and traced in description'of operation of the system.

Generator I comprises a self-starting alternating current motor 3| having flywheel 32 to retard acceleration and centrifugal device 33 similar to ply current to the commutator 9 which by insulated brushes 41 and 48, carried by arms on motor shaft 49, connects the said batteries in sequential manner to the output conductors 4|, 42 by engagement with the short commutator segments 52, 53, and 54. When the commutator brushes are in positions shown, a circuit path will be formed through positive battery 45, segment 5|, brush 48, ring 44, and conductor 42. When brushes '4? and 48 shall have moved through an angle of 45, brush 48 will disen- I gage from the segment 5| and will rest upon an isolated segment while brush 41 will engage segment 5| to form a circuit path through positive battery 45, segment 5|, brush 41, ring 43, and conductor 4|. moved 99 from the position shown, brush 48 will engage segment 52 forming a circuit path through negative battery 45, segment 52, brush 48, ring 44, and conductor 42. When the brushes shall have moved 135 from the position shown, brush 4! will engage segment 52 forminga circuit path through negative battery 58, segment 52, brush 47, ring 43, and conductor 4|. This sequence of four electrical impulses will be repeated through segments 53 and 54 resulting in repeated cycles each comprising a positive impulse on conductor 42 followed by a positive impulse on conductor 4| followed by a negative impulse on conductor 42 followed by a negative impulse on a conductor 4|, completing the cycle.

Lamp 35 glows when motor 3| is rotating at any speed. Shaft 49 carries a worm 5| engaging a gear 52 upon a snail 63 whose follower 64, pivoted at upon a pivoted armature lever 68 of snail magnet '57, engages the snail when magnet 5I is energized and is driven by the snail to engage and close contact members 58, see also Fig. 5. In operation, motor 3| is started by armature 3| of relay 38 and rotates for a counted number of revolutions as determined by snail 55 before the operation of closing the contacts 58.

At substation motor l2 comprises a permanently polarized two-pole rotor and a fixed field structure having four polar field faces with four windings connected serially in pairs. Mounted on the rotor shaft II is a centrifugal device l3 controlling a switch I4 which comprises contact members I2 to 78 inclusive, and having further a rotary cam- I7 controlling a switch I5. A correcting circuit including grounded battery, resistor l8, winding of relay 22, contact of relay 24, line conductor 2|, contact members 13, 14, cam switch I5 when closed, and two field wind- When the brushes shall have ings of motor I2. will supply to motor l2 a current suflicient to turn the rotor into that angular position wherein cam I1 opens cam switch I5, thus interrupting the described circuit. Cam switch I5 determines the angular stopping position of the rotor, thereby eifecting its purpose of opening the line 2| after removalof plug I from jack 8 so that key l8 may be used for signaling.

An operator key 8| is connected to include into the communicative circuit of the plugs I and 2 an operator set comprising recorder 82 and transmitter 83. During a connection between two lines, slow-to-release relays 84 and 85 hold their armatures attracted in response to signaling currents of communicative nature through the plugs and 2. Induction coils having primary windings connected to a common alternating current source it have also secondary windings 88, 89, which supply altemat- .ing current to the circuits of the lines connected to plugs I and 2 for purpose of synchronizing to illuminate lamp 23 ing this line.

- i2 over 45 clockwise from the position shown, a circuit and driving substation motors I2 over circuits to be described.

Operation of the structure illustrated in Fig. 1 is as follows: An operator at substation desiring to transmit a message to a substation on line 94 connected to line jack 95 will operate the calling key -|8 to close a calling circuit including grounded battery, resistor 78, winding of relay 22, contacts of relay 24, line conductor 2|, key I8, and ground, thus energizing relay 22 over an obvious circuit, and thereby producing a visible signal to attract attention of a central ofllce operator serv- The central office operator awaits termination of the lamp signal and then responds by inserting plug i into jack 8 which closes an obvious sleeve circuit of the jack including windings of relays 39 and 24. Relay 24 energizes to prevent reenergization of relay 22 and ,to clear conductor 2| for transmission purposes. Relay 39 energizes. and by its armature contacts energizes relay 59 over an obvious circuit. tracts its armatures and armature |94 energizes snail magnet 67 over an obvious circuit while armature 37 closes an alternating current power circuit for motor 3| which begins to rotate and continues rotation with increasing speed.

Soon after beginning of rotation, centrifugal switch 34 closes an energizing circuit for lamp 35. Generator 7 now supplies a varying polyphase current comprising alternating potentials of increasing frequencies to the output conductors 4|, 42, which now supply current to motor two paths as follows: With brushes 41, 48 in position shown, a circuit path extends from positive battery 45, through segment 5|, brush 48, ring 44, output conductor 42, armature I98 of relay 5, ring members of plug and jack 8, line conductor 2|, and switch contacts l3, 74 to the open cam contact I5. Brushes 41 and 48 may start from any angular position of shaft When brushes 4? and 49 reach a position Relay 38 atis formed from positive battery 45, through segment 5|, brush 41, ring 43, output conductor 4|, back contact and armature I95 of relay 5, line winding I96 of relay 38, tip members of plug I and jack 8, line conductor I01, contact members 15, i5, and two field windings of motor |2.to ground, energizing motor I2 to turn its rotor through thus closing cam switch I5. This is followed by current over a circuit including negative battery-46, segment 52, brush 48, ring 44, output conductor 42, back contact and armature I08 of relay-5, ring members of plug I and jack 8, line conductor 2|, contact members I3, I4, closed cam contacts I5, and two field windings of motor I2 to ground, energizing motor I2 to turn its rotor a further 90. brushes of commutator 9 form a circuit from negative battery 46, segment 52, brush 41, ring 43, output conductor 4|, back contact and armature I05 of relay 5. line winding I05 of relay 38, tip members of plug I and jack 8, line conductor I01, contact members I5, 16 and two field windings of motor I2 to ground, energizing motor I2 to turn its rotor through an additional 90. This is followed by current over a circuit including positive battery 45, segment 53, brush 48, ring 44, output conductor 42, armature I08 of relay 5. ring members of plug I and jack 8, line conductor 2|, contact members I3, 14, closed cam switch I5, since cam I1 now is 90 from its operating angle, and two field windings of motor I2 to ground, producing a field magnetization in motor I2 which will advance the rotor a further 90" completing one revolution of the motor I2. In the second half of the revolution of commutator 9. segments 53 and 54 cooperate with brushes 41 and 48 to repeat impulses of reversing polarity over conductors .4I and 42 and line conductors I01 and 2| to repeat the cycle of the rotor oi Further rotation of the- 4|, 42 equals or exceeds the frequency of currents obtainable from source of alternating current power I0, and the speed of rotation of motor I2 equals or exceeds the speed obtainable from the alternating current power source I0.

Should the brushes of generator I start from any position other than the position shown, the described starting of motor I2 will be delayed by a fraction of a cycle only.

As the speed of the rotor of motor I2 approaches the speed of the alternating current power source I0, the centrifugal device I3 will operate its switch I4 to reverse the contactual relations of contact members 12 to I6 and will remove cam II from engagement with switch I5 as illustrated in dotted line in Fig. 4. By reversal of contact members I2 to 16, an alternating current power circuit for continuous running of motor I2 is set up including batteries 45 and 46 in alternation, segments 5|, 52, 53 and 54 in rotation, brush 41, ring 43, output conductor 4|, back contact and armature I05 of relay 5, line winding I86 of relay 38, tip of plug I, short spring of jack 8, line conductor I0'I, condenser I9, and two field windings of motor I2 to ground. Remaining windings of motor I2 are not used after starting, their circuit path being open at contact I4.

At the same time, by operation of centrifugal switch I4, 2. telegraphic signaling path is formed including batteries 45 and 46 in alternation, segments 5|, 52, 53, and 54 in rotation, brush 48, ring 44, output conductor 42, back contact and armature I08 of relay 5. ring of plug I, long spring of jack 8, line conductor 2|, switch contacts I3, I2, telegraph receiver magnets I6 and telegraph transmitter I I to ground. The telegraph receiver I6 may operate irregularly.

Soon thereafter, snail follower 64 engages and closes snail contact members 58, thus completing a circuit for energization of snail relay I II including grounded battery and resistor II2, Winding of relay I I I, armature N3 of energized and armature relay 38, and contact members 88 to ground. Relay III operates its armatures and energizes relay 5 over a circuit including battery and resistor II4, armature II! and contact of relay III, winding of relay 5, and back contact and armature of unenergized relay 84 to ground. Relay 5 operates its armature I22 to interrupt the energizing circuit of relay 38 while its armature I08 forms an energizing circuit for slow-to-operate relay 84, the relay 38 releasing quickly to close an alternative ground connection through armature I23 for the described circuit of the winding of relay 5 before the slow-to-operate relay 84 has operated its armature to interrupt the original energizing ground contact just described for relay 5. Also, by its armature I24, deenergized relay 38 forms a holding circuit for relay III including grounded battery, resistor II2, winding and contacts of energized relay III, armature I24 and ground. Also, by release of its armature I04, relay 38 interrupts the energizing circuit of snail magnet 61 causing release of pivoted armature 66 which withdraws snail follower 64 from snail 63 whereupon the follower is retired by its spring and permits contact members 68 to separate. Also, by release of its armature 31. relay 38 interrupts the power circuit of motor 3|, the motor stops and lamp 35 is extinguished, thus placing generator I in condition to operate again in response to insertion of plug 2 into jack 95.

By energization of relay 5, a definitive alternating current power circuit has been formed for motor I2 including grounded battery I3I, induction coil winding 88, front contact and armature I05, line winding I08 of relay 38, tip members of plug I and jack 8, line conductor I03, condenser I9, and two windings of motor I2 to -ground. No direct current flows because of condenser |9 hence relay 38 is not energized. Adefinitive telegraphic communication circuit also has been formed by operation of relay 5 including grounded battery, resistor I32, winding of repeating relay I33, contact and armature of energized repeating relay I34, contacts of operator key 8|, winding of relay 84, front contact and armature I08, ring members of plug i and jack 8, line conductor 2|, contact members I3, I2, selector magnets I6 of a recording receiver and contacts of permutation transmitter II to ground. In this circuit, a central office operator may include magnets 82 of a recording receiver and contacts 83 of a permutation transmitter by means of key 8i.

In the circuits of repeating relay set 3, preliminary energizing conditions for the repeating relays I33 and I34 have been provided by two preliminary circuits, one circuit including grounded battery, resistor I32, winding of relay I33, contact and armature of energized relay I34, contacts of manual switch BI, resistor I35, and armature I36 of unenergized relay 5 .to ground, and the companion circuit including grounded battery, resistor I37, winding of relay I34, contact and armature of energized relay I33, resistor I38, I38 of unenergized relay 6 to ground. In the circuits of the repeating relay set 3 as now established, energization of relay 5 interrupts the described preliminary energizing circuit of relay I33 and substitutes the definitive telegraphic communication circuit described above.

The central oflice operator, having operated key 8|, having communicated with calling substation II, and having ascertained that the operator at substation II desires to be connected to ,ingly, relay I63 releases its armatures.

line 84. now establishes the connection by inserting plug 2 in line jack 85, which results in energizing relays |4| and I42 over the sleeve circuit of jack 95. Operation of thearmature of relay I42 corresponding to relay 39 of plug I energizes relay I43 corresponding to relay '38 of plug I.

Relay I43 by armature I44 energizes motor 3|, and by armature I45 energizes snail magnet 81 so that generator 1 again starts and delivers current from its output conductors 6|, 42 through back contacts and armatures I48, I41, of relay 6 and winding I48 of relay I43 to plug 2 and to the line conductors 94 and I59 and substation I5I associated with jack 95. In response to this starting current of varied frequency, the motor at the substation I5I is started and operates its centrifugal device corresponding to I3,of substation II. Snail follower 64 closes snail contacts 68, thus completing a circuit through armature I52 of relay I43 to energize snail relay I53 whose armature I58 responsively closes a circuit through grounded battery, resistor I55, armature I56 of relay I53, winding of relay I5, and armature'of relay 85 to ground to energize relay 6, which by armature I39 opens the described preliminary energizing circuit of repeatingrelay I3 3, by armature I51 interrupts the energizing circuit of relay I33, and by back contacts and armatures I56, I51 interrupts the circuits of output conductors 5|, &2 of generator 1, while by front contact and armature I46, it forms a definitive alternating current power circuit including grounded battery I58, induction coil secondary winding 89, front contact and armature I 48 of relay 5, winding I68 of relay I43, tip of plug 2, short spring of jack 95, line conductor I59 to substation I5I, and through condenser and motor to ground as in substation II, and by front contact and armature I II, the relay 5 forms a definitive telegraph communication circuit including grounded battery, resitsor I31, winding of repeating relay I35, contacts of energized repeating relay I33, winding of slow-to-operate relay 85,

front contact and armature I 61, ring of plug 2,

long spring of jack 95, line conductor 35 to substation I5I and through receiving and recording apparatus to ground as in substation II.

Armature I51 deenergizes relay I53, armature I46 supplies alternating current but does not energize relay I33 to hold its armatures.

Armature I56 provides ground for the winding of relay 6 before slow-to-operate relay 85 opens its ground connection, armature I6I forms a holding circuit for relay I53, while .armatures I 34, Hi5

open their circuits to deenergize motor 3! and snail magnet I51, .thus stopping the motor 3|, extinguishing lamp 35 and restoring arm 541.

'The two substations, both illustrated by details shown in substation II, are now in communication over the circuits described by means of repeating relay set 3, and the motors thereof are maintained at exact speed by currents derived from alternating source III and distributed to the substations over the described alternating current power circuits.

Relays 84 and I34 now are energized by communiwtion signaling currents of marking nature flowing to substation II through jack 8, while relays 85 and I33 are energized by similar currents through jack 95. Relays 26, 39, I II, and I62 are held energized by sleeve circuits of plugs I and 2. Relays 5 and 8 are held energized by ind v dual holding circuits under control of con- Accord- I iii tacts in unenergized relays 38 and I43 respectively.

Means is provided for restarting automatically a stopped substation motor during communicative condition. Should either substation motor or both of them for any cause as by a line fault become out of phase with its power source I. or for any other reason come to rest, or lithe motor should slow down to a speed below that necessary to keep the centrifugal device I3 operated, contacts 15, 16 will shunt the condenser I9. This will permit direct current from battery I3I to flow through the power circuit described, resulting in energization of relay 38 to attract its 'armatures which will set up the starting con ditions of generator I with release of relay 5. so that output conductors 4|, 42 again will deliver to motor I2 polyphase currents oi increasing frequency to bring the motor again into phasing speed with the source III when the centrifugal device I3 and the snail contact 58 again will function to energize relay 5 or 6 and deenergize relay 38 or I43, thus restarting the substation motor and reestablishing the communicative condition.

There are provided a plurality of complete equipments of generator I and motor 3|, one for each connective pair of plugs,-one such pair being illustrated by plugs I, 2.

Referring to Fig. 2, the system therein illustrated utilizes for driving the telegraph apparatus at the substation a motor in which there is provided a permanent field and a distributed winding with a segmented commutator, and in which there also are provided collecting rings connected to a further synchronous winding as illustrated in Fig. 3. Direct current for starting the motor is transmitted over the two sides of the line in parallel and subsequently alternating current is transmitted over the two sides of the line in parallel for driving and synchronizing, while telegraphic signaling current is transmitted over the two conductors of the line looped in series.

At the substations 280 and 256, the motor 2I3| comprises a permanent magnetic field and a rotor 202 having a distributed winding connected to a segmented commutator 2E3. Collecting rings 206 are connected to a further winding in the rotor. A centrifugalswitch 205 operates when the motor is substantially at synchronous speed with source 255 and contains switching elements 206 to 2H] which control substation circuits for line conductors 2H and ZIZ. In the illustrated normal position of the centrifugal switch, assumed when the motor is inert, line conductor MI is connected through winding 2|3 of relay 2| 4, switching element 201 and commutator 203 to ground. Line conductor 2|2 is open to direct currents.

Line conductors ZII and 2|2 are connected through condensers H5 and 2I8 to brushes of collecting rings 265. A manual key 2I1 serves to control signal devices at a central office or switching station to attract attention of an operator. Selector magnets 2I8 symbolize a complete recording receiver, and contacts 2I9 symbolize a Circuits for the described apparatus parts will be disclosed in a description of operation of the structure illustrated in Fig. 2.

At a central station 225, equipment for the line 2| I, 2|2 comprises a jack 226, a cut-off relay 221, a calling line relay 228, and a calling line lamp 229. A pair of connective plugs 23I, 232 are as- I 255 having a frequency higher than baud value of permutation code transmission and windings oi the same induction coils are included in power circuits and telegraphic communication circuits to be described. An operatorfs telegraph set 256 may be switched into circuits of the plug pair 23! 232 by means of manual key 251. Resistor 253 balances against the operator set 256, resistor 259 balances against repeating relay 239, and resistor 260 balances against repeating relay 240. A second substation line 26!, 262 is indicated in association with jack 263 and substation 264 to duplicate the substation 200. Preparatory energizations' of repeating relays 239 and 240 are effected for relay 240 by current over a circuit 265 including grounded battery 245, re-

current from battery 214 as a source 01- motor starting current and carrying aisoalternating source of motor synchronizing current.

parallel motor starting circuits extend for both sistor 24!, winding of repeating relay 239, contact and armature of energized repeating relay 240,

contacts of manual key 251, resistor 255, circuit conductor 265, back contact and armature of sleeve relay 25!, and ground, and for relay 239 over a companion circuit 266 including grounded battery 246, resistor 242, winding of repeating relay 240, contact and armature of energized re, peating relay 239, resistor 261, circuit conductor 266, back contact and armature of relay 252, and ground.

Operation of th: structure of Fig. 2 is as follows: An operator at substation 200 closes the manual key 2!1 thereby energizing signal lamp relay 228 over a calling circuit including grounded battery, resistor, winding of line relay 223, contacts of cut-oif relay 221, line conductor 2!2, key 2H and ground. Contacts of energized relay 228 cause illumination of lamp 229 over an obvious circuit.

An operator at the central oflice 225 awaits cessation of the illumination of lamp 229, then inserts plug 23! into jack 226, energizing sleeve relay '25i and cutoif relay 221 overan obvious circuit. Energization of'sleeve relay 25i opens circuit 265 and thereby interrupts the described preparatory energization of repeating relay 239 whose deenergization changes the energizing circuit of repeating relay 240 from the described preparatory circuit 266 to a holding circuit including ground, resistor, winding of repeating relay 240, make-beiore-break contacts of deenergized repeating relay 239, resistor 244, and

' ground.

Insertion of plug 23! also results in energize.- tion of relays 254,- 233, 235, and reenergizationof relay 239 over a line circuit of first response including grounded battery, resistor 24H, winding 01 repeating relay.239, contact and armature of energized repeating relay 240, contacts of manual key 251, induction coil winding. 21!, winding 212 of relay 235, make-before-break contacts of relay 233, winding 213 of relay 233, tip of plug 23!, short spring of jack 226, line conductor 2! I, winding 2!3 of relay 2l4, contact and switch member 201, commutator 203, and ground. Operation of relays 2 and 233 interrupt the described line circuit of first response and substitute two parallel motor starting circuits each carrying direct current from induction ooilwinding 215 as a The classes of current from ground, through battery 214, induction coil winding 215, both oi the makebefore-break armatures and long contact members or operated relay 233, both windings of relay 233, tip and ring of plug 23!, both springs of jack 226, and both line conductors 2!! and 2!2 to junctions 211, 218 respectively at substation 200. extending thence i'or alternating currents through. condensers 2!5, 2!5, collecting rings 204 and ground, andextending for direct currents from Junction 211, through an energizing winding 2!3 of relay 2, contact and switch member 201 and commutator 203 to ground, also from junction. 216, through contacts of energized relay 2!,4, switch contacts 2!0, 209, winding 219 of relay 2, contact and switch member 201 and commutator 203 to ground. Direct currents start the rotor 202 and drive it with increasing speed until synchronism with source 255, through inducdirect current ceases in windings oi relays 2 I and 233 and those relays are deenergized, resulting in establishment of a first communication circuitand of definitive parallel alternating current power circuits. The first communication circuit includes grounded battery 245, resistor 24!, winding of repeating relay 239, contact and armature member of repeating relay 240, contacts of manual key 251, induction coil winding 21!, winding 212 of relay 235, make-before-break contacts and winding 213 of relay 233, tip of plug 23!, short spring of jack 220, line conductor 2! i, junction 211, windings oi selector magnet 2i-8, contacts of code transmitter 2!!), break key 290, centrifugal switch member 208 and its-long contact spring 2!!], contact and switch member 206, Junction 218, line conductor 2i2, long spring of Jack 226, ring of plug 23!, winding 28! and makebefore-break contacts of relay 233, winding 282 of relay 235, resistor 259 (to balance winding of relay 239), closed contacts 285 of manual key 251, induction coil winding 283, and ground. Differential relay 233 is not energized. Relay 235 is energized and. closes an obvious circuit toilluminate lamp 284 to indicate to an operator at set 256 that the described circuit has been completed. 'Ihedefinitive synchronizing power circuits extend from ground, through induction coil winding 283, closed contacts 285 and resistor 259, to winding 282 of relay 235, and from grounded battery 245, through resistor 24!, winding of repeating relay 239, contact and armature oi energized repeating relay 240, contacts of manual key 251, and induction coil winding 21! to winding 212 of relay 235, thence through windings of relay 235, through make-before-break contacts of deenergized relay 233, windings of relay 233, tip and ring elements of plug 23! and jack 226, line conductors 2!! and 2!2, condensers 2!!: and 2!6, then uniting and continuing through collecting rings. 204 to ground. Relay 23.3 is magnetized to an lnsumcient degreeby the'transmitted' alternating power current, and its armature members are not operated.

The paths for alternating current constitute a phantom channel upon the line it l-tli which is operatively independent of transmission of telegraphic signals over the described telegraph communication circuit, in which signals are orlg inated at substation 2w by substation transmitterditl, and at central station 225 by contacts of repeating relay 2% or by contacts of transmitting relay 28$ responsive to transmitter 28W in operators set 26?. When contacts oi repeating rethe power circuit effectively unchanged. Re-

sistor 269 is included in series in one side of the phantom circuit of plug 2st to balance resistor 2M and winding of relay 239 in the other side 01 the phantom circuit of plug 28L while resistor 2th is included in series in one side of the phantom circuit of plug 282' to balance resistor 262 and winding of relay 2 5s in the other side of the phantom circuit of plug 232. When manual key 251 is operated to include operator's set 258 and. its selector magnet 2st in the telegraph communication circuit and, therefore, in one side of the phantom circuit of plug 23L its contacts 285 open a shunt thereby to include a balancing resistor 25s in the other side of the phantom circuit of plus 2M to maintain balance between the two sides and then when'transmitting relay rot is operated with key 251 in reversed condition,

a resistor 289 to ground is substituted for winding of relay 239, resistor 2M, and battery 2% to ground.

Having inserted plug 28d into-jack 225 in manual response to illumination of signal lamp 229, a switching operator awaits illumination of sig= nal lamp 286, which will not become energized until after the connected substation motor 2M has attained its synchronous speed with result= ant deenergization of relay 233 and energization.

of relay 235. Key 251 then may be operated, thus connecting set 258 and substation 2st for communication, and the switching operator may complete a communicative connection between two substations by inserting plug 232 into any substation Jack ass. After a cycle of operation I to start the motor at substation 264, relay 286 will be energized and lamp 29! will be illuminoted, the two lamps 28d and 29! then functloning to advise the switching operator that the two substations 20d and 264 are connected and conditioned for communication. Either station may operate a break key 290 to control relay 235 or 286 to flash lamp 284 or 29! intermittently to attract attention of the operator.

Referring to Fig. 3, a structure is disclosed in I which local substation power either direct current or altenatlng current is supplied to energize the substation motor and in which the local power is supplemented by alternating current from a central power supply which is transmitted over the phantom circuit of the line for synchronization only. Local power at the substation is applied under control of the transmitted central power through a relay responsive to alternating currents received over the phantom from the central ofllce.

At substation 306, .a driving motor 30! .com-

Y accuser 7/ direct or alternating current, also'a further rotor winding 808 and collecting rings St? for driving the motor by alternating current. The motor is provided also with a centrifugal switch member 3% and electrical switch 899 which is operated when the motor reaches its synchronous speed and remains operated throughout the ensuing communication. A. motor control relay one has its contact and armature connected in the local power circuit of the motor and when energised. closes the circuit oi the local current winding of the rotor. Line conductors 8M and 8!?! are connected through condensers tilt) and sec to winding of relay Bill and through centrifugal switch 8% and "its contact to ground. Selector magnets 8M5 representing a recording receiver and contacts 2386 representing a code signal transmitter are bridged permanently from conductor Sit to conductor 862. A manual calling key on is connected between conductor 382 and ground. A break hey did is provided.

At the central ofiice 820, a pair of connective plugs set and 822 are connected together through a repeating relay set 823, comprising repeating relays 825i and 829 and resistors 8526, 232i, 828, and 829. Included also between plugs" 82! and 822 are a manual key 882 and two induction coils 588 and 8% whose primary windings are associated with a source of alternating current 836,

currences.

Keys 332, 836 are associated by circuits with an operator set 8M comprising a double-wound selector magnet 3&2, a code transmitter-3418, a resistor 366, transmitting relay 3% having makebeiore-break contacts. Plug tti also is provided with a double-wound relay MS, a signal lamp 8st, and a resistor 8438. It is intended that the plug 522 be similarly equipped.

Line iii i--3i2 has central omce equipment comprising a jack est, a calling relay ass, and a calling lamp Slit. Jack ass represents another complete line structure similar to jack 236i and line til-3E2. Preparatory circuits for energization of repeating relays 324 and 825 include grounded battery, resistor 827, winding of repeating relay 3%, contacts of repeating relay 32 3, contacts of key 832, contacts of relay M8 and resistor 348 to ground, also battery, resistor 323, winding of relay 324, contacts of relay 32!, contact oi double-wound relay 385, and resistor to around.

In operation, closure of key 3H energizes calling cults. An operator at the central oilice responds by inserting plug til into jack 35! thereby forming circuits for both direct current and alternating currents. For. direct current, the vcircuit includes grounded battery, resistor 321, winding oi repeating relay 32!, contacts of energized repeating relay 324, contacts of key 332, a lowest winding of induction coil I33, lower winding 0! relay m, ring of plug 32L long spring of Jack 369, line conductor 302, break key M8, normally closed contacts of permutation transmitter 3|. recorder magnets 3, line conductor Ill, short spring oi lack "I, tip of plug Iii, upper winding of relay 5, middle winding of induction coil 333, contacts of key 332, and resistor 368 to ground, energizing relay 3 which closes an obvlous circuit to illuminate lamp 841.

For alternating currents. a circuit includes line conductor 3i2, condenser 3l4, alternating current relay 310, and switch 309 to ground, also a companion circuit includes ground, resistor 38l, contacts of key 332, middle winding of induction coil 333 as a source of alternating current, upper winding of relay 34B, tip oi plug 32!, short spring of Jack 35!, line conductor 3, condenser 3l3,

, alternating current relay M0, and switch 303 to ground, thus energizing relay 310 whose contacts connect commutator 304 and rotor winding 305 to a source 01' current 362. The rotor 303 starts under energy received from source 362 and when operating speed is reached, the centrifugal switch 303 operates to include the rings 301 and winding 306 in the circuits for alternating currents traced above. Alternating currents over a phantom circuit including conductors 3, M2, and earth now synchronize the rotor 303, and communication may be effected. The phantom circuit is balanced at substation 300 by matched condensers 3I3 and 3H, and at central ofllce 320 by two windings of relay 346, by two secondary windings of induction coil 333 and by resistor I balanced against resistor 321 and winding of repeating relay 325.

An operator at central oflice 320 now may operate key 832 by rotating a cam 363 through an angle of 90, thereby connecting receiver magnet 342 into the described line and phantom circuits in balanced manner and including also contacts of transmitting relay 345. Thereafter, communication may proceed between operator set 3 and substation 300. Opening the contacts of transmitter 3l6 to produce a spacing signal does not unbalance the phantom circuit, and opening the contacts of transmitter 343, to produce a spacing signal, operates relay 345 to substitute resistor 344 in place of resistor 321 and winding of relay 325 thereby maintaining the phantom circuit in balance.

A connection for intercommunication between two substations is completed by inserting plug 322 into jack 354,, energizing relay 385 and illuminating lamp 366. At either connected substation, the substation operator may attract attention of the central oflice operator by opening a break key 318, deenergizing one of the doublewound relays 345 and 365 to extinguish one of the signal lamps 341 or 366. Responsively to operation of a key 3|8, a lamp may be flashed repeatedly until a central omce operator answers.

Other applications of the invention as defined by the appended claims may be made in full or ing from said starting means to said running means.

2. In a motor control system, a motor at a substation, a source of alternating current at a central station,a line connected to said motor and extending to said central station, a polyphase generator at said central station, starting circuits for said motor including said polyphase generator and in part as required to practice the invention to any desired extent.

What is claimed is:

1. In a motor control system, a substation motor, a central ofiice, a line connecting said substation to said central ofiice, means comprising a starting circuit at said substation and a line conductor for starting said motor, means comprising a running circuit at said substation and a line conductor for running said motor after starting, means at said substation responsive to the speed of the motor for changing from said starting means to said running means, motor starting means at said central oflice, motor running means at said central oflice, and means at the central office responsive to revolution counting means at said central ofllce for changsaid connecting line, starting means for said polyphase generator, means for connecting said line and motor to said generator while said generator is at rest, and automatic means operating to disconnect said line and motor from said polyphase generator after a predetermined number of revolutions of said generator and to connect said line and motor to said alternating current source.

3. In a communication system, a substation, a central station, electrical connections between the substation and the central station, motor driven apparatus at the substation, means including the electrical connections to start the motor, a motor synchronizing circuit, and automatic means effective after the lapse of a time interval predetermined by apparatus wholly at the central ofiice to establish the motor synchronizing circuit.

4. In a telegraph system, a remote station, a central station, a channel connecting said stations, 9. driving motor at the remote station having a starting and a running condition and connected to said channel, a source of power at said central station for driving said motor, means for connecting said source of power to said channel to effect starting of said motor, means at the central station operated following the starting of said motor for establishing a running condition for said motor, and means responsive to an inert condition of said motor after the establishment of the running condition for reestablishing the starting condition for said motor.

5. In a telegraph system, a central station, a motor at a station remote to said central station having a starting and a running condition, a starting circuit and a running circuit connecting said motor to the central station, means at the central station for changing through said circuits from starting to running condition for said motor by disconnecting said starting circuit and connecting said running circuit, and means operated by the motor upon failure of the motor to maintain a predetermined speed to change from said running condition to said starting condition by reestablishing said starting circuit.

6. In a telegraph system, a central station, a

' motor at a station remote to said central station having a starting and a running condition, a starting circuit and a running circuit connecting said motor to the central station, means at the central station for establishing over said starting cincuit a condition to start said motor, means also at said central station operated in response to a predetermined condition after starting said motor for rendering said starting circuit ineffective and for establishing the running condition for said motor over said running circuit, and a centrifugally operated switch at said motor to interrupt said running circuit and to reestablish said starting circuit upon failure of the motor to maintain a predetermined speed whereby said starting condition is reestablished.

7. In a telegraph system, a central station, a motor at a station remote to said central station having a starting and a running condition, a starting circuit and a running circuit connecting said motor to the central station, means at the central station for changing from starting to running condition for said motor, a relay in said running circuit to interrupt said running circuit, meansin said running circuit to prevent the operation of said relay during normal running condition of said motor, and means at said motor" responsive to a failure of said motor to maintain a predetermined speed to render said last-mentioned means inoperative and to reestablish the starting condition over said starting circuit.

8. In a telegraph system, a central station, a motor at a station remote to said central station having a starting and a running condition, a starting circuit and a running circuit connecting said motor to the central station, means at the central station for changing from starting to run ning condition for said motor, a relay common to both circuits to interrupt saidrunning circuit and reestablish the starting condition over said starting circuit, a condenserin said running circuit to prevent operation of said relay over said running circuit, a circuit shunting said cone denser, and means responsive to a failure of said motor to maintain a predetermined speed on running condition to close said last-mentioned circuit and to operate said relay over said running circuit whereby the starting circuit is reestablished.

9. In a telegraph system, a central station, a motor at a station remote to said central station, a starting circuit and a running circuit connecting said motor to the central station, means at said central station for establishing over said starting circuit a starting-condition for said m0- tor, means also at said central'station operated in response to a predetermined starting condition for rendering said starting condition ineifective and for establishing a running condition for said motor, means at said motor to interrupt said running circuit and reestablish said starting circuit, and speed responsive means at said motor to render said last-mentioned means operative upon failure of the motor to maintain a predetermined speed under running condition.

10. In a telegraph system, apparatus to be driven, a motor for driving said apparatus, a main source of power for driving said motor, an auxiliary source of power for driving said motor having speed controlling characteristics, a circuit including said auxiliary source of power and means responsive to said source of auxiliary pow- 7 er to connect said main source of power to the motor to start said motor, and means operable when the motorattains a predetermined speed for connecting said auxiliary source of power to said motor.

11. In a telegraph system, apparatus to be driven, a motor'for driving said apparatus, a

main source of power for driving said motor, an

auxiliary source of power having motor speed controlling characteristics for driving said motor, a circuit for interconnecting said auxiliary source of power. and said motor, a relay in said circuit responsive to said source of auxiliary pow-- ing said motor to the central station, a variable frequency generator in said starting circuit, and means at said central station responsive to a predetermined number of revolutions of said generator to establish a condition whereby said starting circuit is discontinued and said running circuit is establshed.

13. In a telegraph system, a central station, a motor at a station remote to said central station, a starting circuit and a running circuit connecting said motor to the central station, a variable frequency generator in said starting circuit, a third circuit eifective to discontinue the starting circuit and to establish the running circuit, and means at said central station responsive to a predetermined number of revolutions of said generator to complete said third circuit and change from the starting to the running circuit.

more M. po 'rs. 

